Heat exchange system with automatic pump control



HEAT EXCHANGE SYSTEM WITH AUTOMATIC PUMP CONTROL 2 Sheets-Sheet 1 FiledAug. 22, 1962 x. sod m mu m 0 W.m mac n e m M 0/ llllllllll ll 0 L m m mM u m w I l I l I I I I I I'll w my mm in 9 mm on Nb r\ r|\ f\ 3 mm 9 r\o F ww W om mm -Zmm \u 8 mm M9. B 1 mm 6 iv mm L in F J r J Lwmcczuxm EI 5 NN em 9 y a J mm 000 owm mm 30 mm 5 mm NAM i o 3,62 33:00 @5965 9 5TR m w u m mk.

ATTO R NEY.

Aug. 24, 1965 P. L. GEIRINGER 3,202,203

HEAT EXCHANGE SYSTEM WITH AUTOMATIC PUMP CONTROL Filed Aug. 22, 1962 2Sheets-Sheet 2 26 T Pressure |=|c;.5 FIG.6

INVENTOR. Paul L. Geiringer Wham y ATTORNEY.

United States Patent 3,202,208 HEAT EXCHANGE SYSTEM WITH AUTOMATIC PUMPCONTROL Paul Ludwig Geiringer, Tuckahoe, 'N.Y., assignor to AmericanHydrotherin Corporation, Long Island City,

N.Y., a corporation of New York Filed Aug. 22, 1962, Ser. No. 218,685 9Claims. (Cl. 165-22) This invention relates to a closed circulation heatexchange system and is particularly concerned with a sensor toautomatically vary the system circulation pressure rate in proportion tothe system demand.

The present system has a source of heat transfer fluid which can eitherbe heated or cooled and is circulated by a pumping means such as acentrifugal pump. The liquid coolant can be refrigerated water, or anaqueous solution such as brine, or an organic liquid medium such asglycol. The system includes a main conduit supply to which is connecteda plurality of individual heat exchange units for individual consumers.The individual heat exchange units are also connected to the returnconduit of the system so that the closed circulation operation iseffected by having the centrifugal pump deliver fluid from either theheated or cooled source through the main conduit, and from there it canpass through each individual consumer and then be returned to the sourcebythe return conduit.

In the illustrated and disclosed embodiment reference is made to aheater source supplying hot Water for a plurality of consumers, eachhaving an individual heat exchange unit including a control valve whichvaries the amount of water through an individual heat exchanger inproportion to the demand of the consumer. This arrangement has been suchthat each control valve would be directly responsive to the heat demand,and if the demand for heat was low, the control valve would close to,throttle the flow thereby decreasing the amount of hot water circulationrequired in the main supply conduit. It should be kept in mind that whena system of this type is installed, the greatest heat demand is firstdetermined, and the capacity and pressure of the pump is set to supplysuflicient hot water for the greatest demand at the farthest point. Asindicated above, when this demand is less than peak capacity, thecontrolvalves will have moved into a throttling'position to reduce the, waterbeing distributed. However, the pump has been set to deliver the supplyfor greatest demand so an excess pumping head is created when the demanddecreases. Such excess head is taken up in the throttling of theindividual control valves, but this is undesirable since it creates aresistance in the system using costly electric power.

The system can also be explained in terms of the pressure drop. Eachindividual heat exchange unit connected along the main conduit requirestogether with the main conduit a certain pressure drop. If all heatconsumers are operating at full demand, then the pump has to operate ata certain number of revolutions to create a sufficiently high pressurehead to satisfy the demand of the main conduit and eachheat consumer. Inthe past the centrifugal pump has been set for constant speedto providefor this maximum demand. Of course this ideal arrangement exists onlywhen the demand of every heat consumer remained constant at maximumcapacity with the control valves nearly wide open. However, in prac ticeit is found that not always maximumdemand prevails for each individualuser, and this results in the individual control valve throttling todecrease the supply which creates an additional pressure head in thethrottled valve while the pumpmaintains its constant head and speed.Attempts *have 'been made to regulate manually the speed of the pump asthe demand varies, but theyhave in- 3,202,208 Patented Aug. 24, 1965volved the use of an operator who had to visit distant heat consumersand from the readings of the gauges of the heat consumers would attemptattempt to set the a proper pump speed. However, this manual operationhas proved of limited success, for the operator has to be highly skilledto interpret the readings and such manual control is tardy andinaccurate so that considerable undesired valve throttling takes placebefore the manual speed con trol can become effective.

Therefore, it is an object of the. present invention to provide a closedcirculation heat exchange system in which a sensor automatically variesthe pressure at the pump outlet in proportion to the demand.

It is another object of the present invention to provide a closedcirculation heat exchange system in which the speed of a supply pump isautomatically varied by a sensing element connected with at least oneindividual heat exchange unit.

It is a further object of the present invention to provide a closedcirculation heat exchange system having a plurality of individual heatexchange units to automatically vary the supply pump capacity by asensing element controlled by the demand of the heat exchange unit mostdistant from the heater.

It is a still further object of the present invention to provide aclosed circulation heat exchange system having a plurality of individualheat exchange units to automatically vary the supply pressure head byany one of a plurality of sensing elements controlling the correspondingheat exchange units.

It is another object of the present invention to provide a closedcirculation heat exchange system that is automatically operated toaccurately deliver only a sufiicient pressure head to satisfy the demandand maintain at least one of the control valves of individual heatexchange units open almost wide.

In practice it is known that when a great many individual consumerconnections are made on an extended hot water heat exchange system, thedemands of the various similar consumers are generally the same at thesame time. In other. words, during the night it is known that the demandon most units will be at a minimum while at a certain time during theday it will be at its highest. Since the various consumers located nearthe end'ofthe line represent a homogeneous mass, an individual unit or asmall group of individual units can be taken as representative of thedemand fluctuations. It is preferable to use the lastheat exchange unitin the line to regulate the system, for if a sensing element associatedwith this last unit provides for proper supply to the last group ofunits, then it follows that the units up the line will be receiving aproper supply also.

In accordance with the present invention there is provided a hot waterheat exchange system having a speed control for a centrifugal pump thatvaries automatically to maintain the delivered supply pressure equalto avarying demand with the control valves for at least one of theindividual heat exchange units close to a Wide open posi- FIG. is anembodiment showing a sensor using a pneumatic control; and

FIG. 6 is an embodiment showing a sensor usmg a wireless control.

Referring to FIG. 1 a heater it) delivers heated water by means of acentrifugal pump 12 to a main supply line 14. A large number ofindividual heat consumers are connected with said main supply line 14,but for ease of explanation only individual units l6, 18, 20, 22 and 24are shown. The individual units are connected between the supply line 14and a return line 26 so that a complete closed operation is representedby the hot water from heater 10 being forced by pump 12 through supplyconduit 14 through the individual units 16-24 to deliver heat, thenreturned in cooled condition by conduit 26 to the heater 10 to bereheated.

Each individual unit is located at a certain distance down the line ordownstream of the heater it As illustrated in FIG. 1, unit 16 is locatedat point A down the line, unit 18 at point B, unit 20 at point C, unit22 at point D and the last unit 24 at point E. As the hot water ispumped along in the conduit 14 and returned through conduit 26, it willbe appreciated that for each point along this conduitva certain pressuredrop exists due to the friction loss in the conduit and the resistancein the individual unit and its control valve. Point E is the farthestalong the line :and therefore can be considered representative of themaximum pressure drop in the supply and return line. Pump 12 must have apressure head sulficient to overcome this pressure drop and theresistance of the unit and 'its control valve. The available pump headtherefore must be of a value equal to the friction loss in the supplyand return lines at the maximum demand of the various individual units.

Each individual unit includes an inlet conduit from main conduit 14 andan outlet connection to return conduit 26. Heat exchanger unit 16 hasinlet conduit 28 and outlet conduit 30. A control valve 32 is located inoutlet conduit 36 and regulated according to heat demand by aninstrument 35 located in conduit 34 connecting valve 32 to the heatexchanger unit 16. Heat exchanger unit 18 has inlet conduit 36 andoutlet conduit 38. A control valve 46 is located in outlet conduit 38and regulated according to heat demand by -an instrument43 located inconduit 42 connecting valve to the heat exchanger unit 18. Heatexchanger unit 20 has inlet conduit 4-4 and outlet conduit 46. A controlvalve 48 is located in Cir outlet'conduit 46 and regulated according toheat demand I by an instrument 51 located in conduit connecting valve 48to heat exchanger unit 20. Heat exchanger unit 22 has inlet conduit 52and outletconduit 54. A control valve 56 is located in outlet conduit 54and regulated according to'heat demand by an instrument 59 located inconduit 58 connecting valve 56 to heat exchanger unit 22. The'last heatexchanger unit 24- has inlet conduit 66 and outlet conduit 62. A controlvalve 64 is located in outlet conduit 62' and regulated according toheat demand by an instrument 67 located in conduit 66 connecting valve'66 to heat exchanger unit 24.

As illustrated in the preferred embodiment of FIG. 1 a sensing element68 is associated with control valve 64 which is connected to the lastindividual heat exchange unit 24. Sensor 68 is connected to conduit 6-2by a pair of connections 70, 72, connection 70 being upstream of controlvalve 64 and connection 72 being downstream of control valve 64. Theseconnections 70, 72 sense the differential pressure between the two sidesof control valve 64 representing the pressure drop across the valve. Ifthe system is calling for full capacity from pump 12, then all controlvalves 32, 4th, 48, 56 and 64 will be wide open and there will bepractically no pressure drop across valve 64'. Under such circumstancesthe sensor 68 will not pick up a signal from the connections '70, '72.

Now if there is a decrease in demand for an individual consumer, such asat the last point B, the instrument 67 will react to this decreasedemandand effect throttling of valve 64. This throttlingaction creates apressure drop across valve 64 which produces a signal in sensor 68. Inthe illustrated embodiment this signal is shown as being transmitted bya connection 74 to. a reversing gear motor '76. The signal may bepositive or negative for driving the reversing gear motor 76 in onedirection or the other to establish an increasing or decreasing speedsetting on a speed control 78, the specific setting being determined bythe strength of the signal in proportion to the throttling. Pump 12 isdriven by a motor (not shown), the speed of which is controlled by speedcontrol 78. Accordingly, the aforementioned decrease in demand is seento create a signal in sensor 68 which will decrease the speed of pump 12so that water is pumped into the system at a smaller head. The decreasedpumping speed is commensurate with the amount of throttling of thecontrol valve and will continue to decrease until the control valve 64is again almost wide open to supply the decreased demand at the presetpressure drop at which time no signal appears in sensor This change insupply can be better understood by referring to FIG. 2 in which theabscissa represents the demand such as in gallons per minute and theordinate represents the pressure head of the pump. Curve 4 represents aplot of the pump head required to provide a maximum fiow in theillustrated system taken at points A, B, C, D and E along the consumerline. Point Y on the abscissa represents the maximum fiow required inthe line with all valves open, and point 6 represents the pump headrequired to supply this demand. The specific values on curve 4 thereforerepresent the pressure loss in the supply and return conduits betweenheater l6 and the most remote valve 64for varying supply conditions.Curve 5 represents the relation of varying water volume pumped and thehead produced by the pump at the maximum pump speed. It is seen that thepump head at the flow volume Y corresponding to point ,6 is sufiicientto overcome the friction loss along the line and supply enough water formaximum demand Y. Accordingly, at point 6 there is no wasted energy orheat from a throttled valve. Now if conditions should change so thatthere'is a decrease from the maximum heat demand, then the system willonly require a flow amount as represented by a point X on the abscissa.If the pump continues to run at full speed, the total pump headavail-able is represented by point 7, but as clearly shown by curve 4the head required tosupply the flow at point X is represented'by point 8When the control valves are wide open. Therefore, it is seen that thepump head between points 7 and 8 is excess and is taken up in thethrottled valves. This excess head is taken up as a heat and frictionloss in the throttled control valves. With the present invention suchexcess head is avoided since as soon as the flow decreases, the sensor68 automatically causes the pump 12 to run at slower speed with asmaller head, and an equilibrium condition of supply and demand isachieved with the control valves wide open as represented by the newpump curve 9 which corresponds to the reduced speed. Curve 9 illustrateshow the lower head of the pump is sufiicient to overcome the frictionloss and accommodate the decreased demand without any excess head.

FIG. 3 illustrates a sensor having a pressure differential control. Inthis embodiment, as in other embodiments hereinafter illustrated, thesame numeralsare used for the same elements shown in FIG. 1. In FIG. 3 achange in heat demand will cause a throttling of valve 64, and thepressure differential on either side of valve 64 is directed throughconnections 76 and 72 to bellows T and V. The difference in pressure inbellows T and V results in movement of contact to which is attachedlever P that is pivoted at point W. Lever P is biased in position by opposing springs M and N so that a predetermined pressure differential isrequired before lever P is moved. The

. movement of lever P actuates a further pivoted lever L which closeseither switch R or switch S depending on which way lever P is moved.Switches R and S are conventional, and operation thereof energizesreversing motor '76 in one or the reverse direction depending on whichswitch is closed. If closing switch R energizes reversing motor 76 toincrease the speed of pump 12, then more hot water will flow, and thiswill decrease the pressure drop around valve 64 and open switch R toautomatically maintain the desired flow around substantially unthrottledvalve 64. A decrease in demand will move lever P in the oppositedirection to close switchS and reverselyienergize reversing motor 76 andreduce the speed of pump 12 to automatically maintain the desired flowaround substantially unthrottled valve 64.

In FIG. 4 a plurality of sensors 68 and 80 are shown connected inparallel to provide the automatic control. Asshown in FIG. 1, thesensingcontrol is substantially at the end of the supply line 14, andthis is true also when a pluralityof sensors are used. Sensors 68'and 80may operate conventional switches R and S as described in connectionwith FIG. 3. In operation any, one of these sensors remote fromthesupply andshown with a parallel connection 82 may provide theautomatic control by sending the appropriate signal to reversing motor76 as described in connection with FIG. 3. i C

It will be appreciated from an examination of FIGS. 1

and 2 that the pumping head decreases proportionately out to the lastconsumer at the end ofthe supply line 14. The automatic controlhereinbefore described provides for maintaining the last control valvesubstantially open, and at the sametime the control valves, such asvalves 32, 40, 48 and 56 operate in a degree 'of throttled conditionpro.- portional to the demand of the particular consumer involved atthat particular location.

In FIG. 5 a sensor using a pneumatic control is illustrated. Bellows Tand V as shown in FIG. 3 are connected around valve 64, and adifierential in pressure moves a pivoted lever 115. This in turn moves aflapper 114 which controls a bleed nozzle 116. A pressure supply Y isprovided which actuates a piston 98 in a cylinder 100 that is biased byspring 102. Movement of piston 98 increases or decreases energization ofreversing motor 76 as described in connection with FIG. 3. It isseen'that a change in heat demand will change the throttlingrelationship of valve 64 and provide a differential pressure in bellowsT and V. This will cause movement of lever 115 and flapper 114 to openor close the pressure bleed from nozzle 116. For example, if nozzle 116is closed, then the pressure supply Y, which may be air or fluid, willactuate piston 98 against the bias of spring 102 which changes reversingmotor 76 and. the speed ofpump 12.

In FIG. 6 is shown a wireless embodiment of the sensor. As described forFIG. 3 switches R and S can be used to provide a signal to transmitter112 or 124 depending on whether there is an increase or decrease in heatdemand. The signal is picked up by either receiver 126 or 118 andreversing motor 76 is changed appropriately.

It will be appreciated that in actual practice the required pump head iscontinually fluctuating, and an eflicient op eration can only besupplied by the automatic control afforded by the present invention.

The particular embodiment of the invention illustrated and described isto be considered illustrative only. For

example, the invention is not limited to hot water systems as other heattransfer fluids for heating or cooling can equally well be used. Thepresent invention includes such other modifications and equivalents asmay readily occur to those skilled in the art, within the scope of theappended claims.

What is claimed is:

1. A closed circulation heat exchange system having a source of hotwater supply connected to a supply line and a return line with a pumpingmeans to force said hot water through said lines for return to saidsource, a plurality of individual heat exchanger units each connectedbetween said supply and return lines with a throttling control valveassociated with each individualheat exchanger unit for controlling theflow therethrough, and means including a pressure differential controlunit having pressure connections on either side of at least one of saidcontrol valves that is located substantially at the end of the supplyline remote from said source of supply to sense the pressurediiferential across said one valve in response to a change in heatingdemand and maintain said one control valve substantially unthrottled byproportionately varying the speed of the pumping means to establishautomatic regulation of the water supply.

\ 2. A closed circulation heat exchange system having a source of liquidcoolant connected to a supply line and a return line with a pumpingmeans to force said liquid coolant through said lines for return to saidsource, a plurality of heat exchanger units each connected between saidsupply and return lines with a throttling control valve associated witheach individual heat exchanger unit for controlling the flowtherethrough, and means including a pressure differential control unithaving pressure connections on either side of at least one of saidcontrol valves that is located substantially at the end of the supplyline remote from said source of coolant to sense the pressuredifferential across said valve in response to a change in cooling demandand maintain said one control valve substantially unthrottled b'yproportionately varying the speed of the pumping means to establishautomatic regulation of the liquid coolant supply..

3. A closed circulation heat exchange system having a source ofrefrigerated water supply connected to a supply line and a return linewith a pumping means to force said refrigerated water through said linesfor return to said source, a plurality of individual heat exchangerunits each connected between said supply and return lines with athrottling control valve associated with each individual heat exchangerunit for controlling the flow therethrough, and means including apressure differential control unit having pressure connections on eitherside of at least one of said control valves that is locatedsubstantially at the end of the supply line remotefrorn said source ofsupply to sense the pressure ditferential across said valve in responseto a change in cooling demand and maintain said one control valvesubstantially unthrottled by proportionately varying the speed of thepumpingrneans to establish automatic regulation of the refrigeratedwater supply.

4. A closed circulation heat exchange system having a source of hotfluid supply connected to a supplyline and a return line with a variablespeed centrifugal pump to force said hot water through said lines forreturn to said source, a plurality of individual heat exchanger unitseach connectedbetweensaid supply and return lines with a throttlingcontrol valve associated With each individual heat exchanger unit forcontrolling the flow therethrough, and means including a pressuredilferential control unit having pressure connections on either .side ofat least one of said control valves that is located substantially at theend of the supply line remote from said source of supply to sense thepressure ditferential across the valve as it responds to a change inheating demand, said means operable to create an electrical signal whensaid pressure difierential exceeds a predetermined value to drive areversing motor to set the speed of said centrifugal pump in proportionto the amount of the heating demand and maintain said one control valvesubstantially unthrottled to establish automatic regulation of the fluidsupply.

5. A closed circulation heat exchange system having a source of hotwater supply connected to a supply line and a return line with avariable speed centrifugal pump to force said hot water through saidlines for return to said source, a plurality of individual heatexchanger units each connected between said supply and return lines witha throttling control valve associated with each individual heatexchanger unit for controlling the flow therethrough,

and means including a pressure differential control unit having pressureconnections on either side of at least one of said control valves thatis located substantially at the end ofthe supply line remote from saidsource of supply to sense the pressure differential across the valve asit responds to a change in heating demand, said means having twoswitches each for controlling an electric circuit, a pressuredifferential across the valve below a predetermined value actuating oneswitch and a pressure diifeerntial across the valve above thepredetermined value actuating the other switch, said switch actuationsending a signal through the circuits to'drive a reversing motor' to setthe speed of said centrifugal pump in proportion to the amount of theheating demand and maintain said one control valve substantiallyunthrottled to establish automatic regulation of the supply.

6. A closed circulation heat exchange system having a source of hotwater supply connected to a supply line and a return line with a pumpingmeans to force said hot water through said lines for return to saidsource, a plurality of individual heat exchanger units each connectedbetween said supply and return lines with a throttling control valveassociated with each individual heat exchanger unit for controlling theflow therethrough, and means including a pressure differential controlunit having pressure connections on either side of at least one of saidcontrol valves that is located substantially at the end of the supplyline remote from said source of supply to sense the pressuredifferential across the valve in response to a change in heating demand,said means operable to actuate a com pressed air device connected tovary a speed control for changing the pressure head of said pumpingmeans in proportion to the variation in the pressure differential andmaintain said one control valve substantially unthrottled to establishautomatic regulation of the supply.

7. A closed circulation heat exchange system having a source of hotwater supply connected to a Supply line and a return line with a pumpingmeans to force said hot water through said lines for return to saidsource, a plurality of individual heat exchanger units each connectedbetween said supply and return lines with a throttling control valveassociated with each individual heat exchanger unit for controlling theflow therethrough, and means including a pressure differential controlunit having pressure connections on either side of at least one of saidcontrol valves that is located substantially at the end of the supplyline remote from said source of supply to sense the pressuredifferential across the valve in response tov a change in heatingdemand, said means operable to transmit a wireless signal to a receivingtransducer on a speed control for changing the pressure head of saidpumping means in proportion to the variation in the pressuredifferential and maintain'said one control valve substantiallyunthrottled to establish automatic regulation of the supply.

8. A closed circulation heat exchange system having a source of hotwater supply connected to a supply line and a return line with a pumpingmeans to force said hot water through said lines for return to saidsource, a plurality of individual heat exchanger units each connectedbetween said supply and return lines with a throttling control valveassociated with each individual heat exchanger unit for controlling theflow therethrough, and means including a plurality of pressuredifferential control units individually connected with pressureconnections on either side of a corresponding number of control valvesthat are located at the end of the supply line remote from said sourceof supply to sense the pressure differential across each valve as itresponds to a change in heating demand, said means first responding tosaid change in heating demand operable to maintain its individualcontrol valve substantially unthrottled by proportionately varying thespeed of the pumping means to establish automatic regulation of saidwater supply. 7 g

9. A closed circulation heat exchange system having a source of hotwater supply connected to a supply line' and a return line with avariable speed centrifugal pump to force said hot water through saidlines for return to said source, a plurality of individual heatexchanger units each connected in parallel between said supply andreturn lines with a'throttling'control valve associated with eachindividual heat exchanger unit for controlling the flow therethrough,and means including a plurality of pressure differential control unitsindividually connected with connections on each side of a correspondingnumber of control valves that are located at the end of the supply lineremote from said source of supply to sense the pressure differentialacross each valve as it responds to a change in heating demand, saidmeans having a first switch for controlling a circuit to drive areversing motor in one directionand a second switch for controlling acircuit to drive a reversing motor in the other direction, said firstswitches connected in series and said second switches separatelyconnected in series, a pressure differential across one of the controlvalves below a predetermined value actuating one of the first switches,and a pressure differential across one of the control valves above apredetermined value actuating one of the second switches, said switchactuation sending a signal to drive said reversing motor to setthe speedof said centrifugal pump in proportion to the amount of the heatingdemand to maintain said one control valve substantially unthrottled toestablish automatic regulation of said water supply.

No references cited.

CHARLES SUKALO, Primary Examiner.

JAMES W. WESTHAVER, Examiner.

1. A CLOSED CIRCULATION HEAT EXCHANGE SYSTEM HAVING A SOURCE OF HOTWATER SUPPLY CONNECTED TO A SUPPLY LINE AND A RETURN LINE WITH A PUMPINGMEANS TO FORCE SAID HOT WATER THROUGH SAID LINES FOR RETURN TO SAIDSOURCE, A PLURALITY OF INDIVIDUAL HEAT EXCHANGER UNITS EACH CONNECTEDBETWEEN SAID SUPPLY AND RETURN LINES WITH A THROTTLING CONTROL VALVEASSOCIATED WITH EACH INDIVIDUAL HEAT EXCHANGER UNIT FOR CONTROLLING THEFLOW THERETHROUGH, AND MEANS INCLUDING A PRESSURE DIFFERENTIAL CONTROLUNIT HAVING PRESSURE CONNECTIONS ON EITHER SIDE OF AT LEAST ONE OF SAIDCONTROL VALVES THAT IS LOCATED SUBSTANTIALLY AT THE END OF THE SUPPLYLINE REMOTE FROM SAID SOURCE OF SUPPLY TO SENSE THE PRESSUREDIFFERENTIAL ACROSS SAID ONE VALVE IN RESPONSE TO A CHANGE IN HEATINGDEMAND AND MAINTAIN SAID ONE CONTROL VALVE SUBSTANTIALLY UNTHROTTLED BYPROPORTIONATELY VARYING THE SPEED OF THE PUMPING MEANS TO ESTABLISHAUTOMATIC REGULATION OF THE WATER SUPPLY.